Wiring device



April 23, 1963 Filed Nov. 3. 1960 FIG. 6.

D.- B. ROBINSON WIRING DEVICE 2 Sheets-Sheet 2 INVENTOR:

DONALD E. ROBINSON ATTORNEY Unite States Patent Office 3,087,135 Patented Apr. 23, 1963 3,087,135 WIRING DEVICE Donald B. Robinson, Webster Groves, M0., assignor to Joy Manufacturing Company, Pittsburgh, Pa., a corporation of Pennsylvania Filed Nov. 3, 1960, Ser. No. 67,131 11 Claims. (Cl. 339184) This invention relates to a wiring device and more particularly to a wiring device having means to prevent mismating of electrical contacts.

At the present time it is common practice in the electrical industry to design electrical receptacles and plugs having a multiplicity of mating contacts which mate in one predetermined way only. For instance, plugs and receptacles exist for use on three phase alternating current circuits having a ground wire provided so that a mating plug and receptacle pair each has four contacts, one -for each phase of the alternating current and one for the ground wire. For such use it is necessary that the plug and receptacle only mate together in one way; otherwise, various dangerous conditions could occur, such as the ground wire from the plug becoming energized by reason of being mis-mated with a hot contact in the receptacle. Such a mis-mating would in many cases, apply voltage to the frame or casing of a tool or machine, or to the body of the plug itself since the plug body is normally, at least in part, formed from an electrical conducting material. Such a mismating of contacts is potentially highly dangerous since people are likely to be or come in contact with the metallic structure which is intended to be grounded but which due to mis-mating is energized. The device of this invention is intended to eliminate the possibility of mis-mating.

Accordingly, one object of this invention is to provide a new and improved wiring device having a plurality of engageable contacts and means for permitting engagement of such contacts in one predetermined manner only.

Another object of this invention is to provide a new and improved wiring device having a plurality of engageable contacts one of which is hollow and is provided with a slidable locking tab to permit engagement of all of such contacts in one predetermined manner only.

A specific object of this invention is to provide a new and improved wiring device having a plurality of engageable contacts one of which is hollow and has a slidably displaceable locking tab therein, which locking tab has an outward projecting portion engageable with the front end of a cooperable wiring device to prevent improper engagement of the wiring devices, and which tab has a portion engageable with the male electrical prong of such cooperable wiring device to prevent such engagement of the projecting portion.

Another object of this invention is to provide a new and improved electrical contact comprising a tubular portion having a locking tab slidable therein and of a structure so that said contact can only be energized in one predetermined manner.

Another object of this invention is to provide a new and improved electrical contact comprising a slotted tubular member having a locking tab slidable therein and biased towards one open end thereof and which tab has means for preventing such sliding movement and means for overcoming such means for preventing such sliding movement.

These and other objects of the invention will become more apparent upon consideration of the following detailed description of preferred embodiments thereof when taken in conjunction with the following drawings, in which:

FIG. 1 is an enlarged end elevational view of a wiring device constructed in accordance with the principles of this invention,

FIG. 2 is an enlarged end elevational view of a wiring device of a structure to engage the wiring device shown in FIG. 1,

FIG. 3 is a partial side cross sectional and partial end elevational view of the wiring devices shown in FIG. 1 and FIG. 2 in their engaged position,

FIG. 4 is an enlarged top plan view of an electrical contact constructed in accordance with the principles of this invention,

FIG. 5 is a partial longitudinal cross sectional view and a partial side elevational view of the electrical contact as shown in FIG. 4, and

FIGS. 6 to 9 are enlarged partial side elevational and partial cross sectional views of the electrical contact as shown in FIGS. 4 and 5 and the wiring device as shown in FIG. 2. showing various relative cooperating positions therebetween.

Referring to FIGS. 2 and 3 an electrical receptacle 2 of known construction with which the structure of this invention is adapted to cooperate comprises a suitably formed elongated insulated housing 4 having a plurality of openings 3 extending longitudinally therethrough which openings 3 are parallel to and located in arcuate spaced relationship about the longitudinal axis of the housing 4. Suitable cylindrical electrical conducting male contacts P and G made of a suitable electrical conducting material such as copper or a copper alloy are suitably rigidly secured to the housing 4 to extend axially within the openings 3; respectively. Although not shown, it will be realized that the male contacts are suitably electrically energizable and that the outer ends are spaced inwardly of the outer face 5 of the housing 4. As shown, the receptacle '2 has three power contacts P and a ground contact G which ground contact G is of a greater length than the power contacts P so that the outer end is located forwardly of the outer ends of the power contacts P. All of the outer ends of contacts P are located in the same plane so that the outer end of the contact G is located closer to the face '5 of the housing 4 than is the outer end of any of the power contacts P.

In general, electrical receptacles, such as receptacle 2, are provided with a ground contact such as G, of a greater length and extending forwardly of the power contacts, such as contacts P, so that the ground circuit is established first and is disconnected last upon engagement and disengagement, respectively, of a receptacle 2 with the Wiring device cooperable therewith. Although not shown it is to be realized that the contacts G and P are each suitably electrically and mechanically secured to the housing 4 and that suitable electrical conductors are connected to the contacts P and G respectively, in any suitable well known manner in the art. Inasmuch as the structure of electrical receptacles, such as receptacle 2, is well known in the art further description and illustration thereof is not believed to be necessary. As is known electrical receptacles, such as receptacle 2, are electrically and mechanically connectable and disconnectable to a suitable connectable receptacle, however, in order to accomplish the purposes of this invention an electrical plug 6 of a novel structure is provided.

As shown in FIGURES 1 and 3 the plug 6 comprises a suitable tubular electrical conducting shell 8 having its rearward end suitably mechanically engaging the outer end of a suitable coaxial tubular insulating sleeve 10. For the purposes of this invention the shell 8 may be made from any suitable material preferably a heat treated aluminum and is rigidly secured in any suitable manner such asby-molding forexample to a sleeve 10 formed from a neoprene molding compound whereby a unitary structure is obtained. The sleeve 10 may be of any suitable structure well known in the art to suitably encompass the fiexible end of a suitable electrical cable, not shown, having suitable flexible electrical insulated conductors 12 extending from the sheathing thereof.

As shown, a suitably generally cylindrical electrical insulating contact body 14 is rigidly secured within the inner end of the shell 8 in any suitable manner such as by a plurality of circumferentially spaced machine screws 15 extending through radially extending threaded openings in the shell 8 with the inner ends of the screws 15 engaging the outer periphery of the contact body 14. A-plurality of suitably elongated electrical conducting female contacts 18 and an elongated electrical conducting ground female contact 20 are suitably rigidly secured in parallel relationship within the contact body 14 to extend axially therethrough in arcuately spaced relationship corresponding to the arcuate spacing of the contacts P and G. Although the body 14 may be formed in various suitable manners the body 14 is preferably a molded body. For such purposes a neoprene molding compound may be employed for the body 14. In order to facilitate the securing of the contacts 18 and 20 within the body 14 the contacts 18 and 20 may be provided with any suitable means such as laterally flared skirts 21 which captively locate the contacts 18 and 20 respectively in the body 14. Each of the contacts 18 and 20 is provided with a suitable terminal portion 24 extending rearwardly of the inner surface of the body 14 which terminal portions 24 are of a suitable structure whereby, after the insulation has been removed, the end portions of the electrical conductors 12 are electrically and mechanically secured thereto, respectively. In addition a suitable ground contact 26-maybe suitably secured such as by rivet 27 'to the'contact 20 which is of suitable form to extend intoengagement with the inner surface of the shell 8 whereby the shell 8 is properly grounded. The contacts'18 and 20 have elongated tubular portions 28 and 29 whichextend from inwardly of the body 14 to the outer end of the contacts 18 and 20 respectively. It will be noted that the tubular portions 28 and 29 of the contacts 18 and 20 are of the same length so that the outer annular surfaces thereof are located in the same transverse plane of the electrical plug 6.

In accordance with this invention'the female contact 20 is of a unique constructionin that the'tubular portion 29 is provided with-a short axially extending slot 30 adjacent the outer end thereof and an elongated slot 32 spaced inwardly from and in axial alignment with the slot 30. Slot 32 extends axially along tubular portion 29 with the inner end thereof terminating outwardly adjacent the outer end of the body '14.- A formed locking tab 34 is slidably receivedwithin the slot 32 and the central opening of the tubular portion 29 so as to be longitudinally slidable therein. As best shown in FIGURE-4 the tab '34 is flat-and of'a width so as to readilyper'mit the insertionof the-tab 34 through the slot 30 into the tubular portion 29 of the contact20.

'In particular it will'be noted (FIG. 5) that the tab 34 is of anirregular shape having a substantially rectangular base portion 36 the upper portion of which is slidable in the slot 32 and the lower portion of which, when in the outward position shown in FIGURE 5, is spaced upwardly from the lower arcuate surface of the tubular portion 29 of the contact 20. A portion 38 is formed integral with the tab 34 which is downwardly offset with respect to the base portion 36 and extendsaxially of the contact 20 and forwardly from the base portion 36 in the tubular portion 29 with the lower surface thereof located closely adjacent the lower arcuate surface of the tubular portion 29 and with the upper surface thereof spaced from the upper arcuate surface of the tubular portion 29 (when the tab 34 is in the outward position as shownin FIGURE 5). It will also be noted that an outer end portion 42 extends upwardly from the portion 38 to form in con-junction with the forward extending; portion 38 a hook with the upper surface thereof en-- gaging the upper arcuate surface to the tubular portion 29. In addition the outer forward edge of end portion 42 is provided with an upwardly and rearwardly sloping: surface 44 which is engaged by the outer end of the: contact G as hereinafter described.

The tab 34 is also provided with an integral upwardly and rearwardly extending generally rectangular projection 46 which slides axially of the tubular portion 28 in the slot 32 and outwardly therealong. Further the tab: 34 is provided with an integral axially inwardly extend-- ing projection 48 which is substantially semi-circular lIli form with the central longitudinal axis thereof locatedl slightly above the longitudinal center line of the tubular portion 29. In order to bias the locking tab 34 outwardly; in the tubular portion 28 of contact 20 a suitable elongated helical coil spring 50' is closely received in the tu-- bular portion 29 between the base thereof and the tab: 34 with the outer end of the spring 50 encompassing the. projection 48 of the tab 34. The spring 50 is of a con-- struction so that when the tab 34 is in the extended position shown in FIGURE 5 the locking tab 34 is biased? to its full outward position with the portion 52 located.

, at the base of the forward edge of the portion 46 engaging the forward end of the slot 32. Such engagement; of the portion 52 with the forward end of the slot 32; serves as a pivot point or fulcrum so that as long as the spring force of the spring 50 is exerted against the tab 34 in a plane below the plane of such fulcrum the tab 34 is biased in "a clockwise direction (with reference to FIG. 5 so that the upper surface of the outer end portion 42 is in engagement with the upper arcuate surface, of the tubular portion 29 of the contact 20.

FIGURE 6' illustrates only the contact 20 structure as: shown in FIGURE 5 and that portion of the receptacle. 2 having the ground contact G therein as they are positioned prior to the insertion of the male ground contact; G into the female contact 20. It will be noted and as. heretofore described that as the contact G is of greater length, the dotted line in FIGURE '6 on the contact G: illustrates the length of the power contacts P in the re-- ceptacle 2. The opening 3 of the receptacle 2 with con-- tact G therein is inserted over the outer end of the t-ubular portion 29 of the contact 20 and is pushed longitu-- dinally therealong until the ground contact G enters the: tubular portion 29 of the contact 20 with the longitu-- dinal axis of the contact G coincident with the longitudinal axis of the female contact 20. It will be appreciated that the contacts P and G are of a diameter to be closely received in the tubular portions 28 and 29 respectively. Upon further longitudinal movement of the contact G into the female contact 20 the outer end of the contact G engages the forward sloping edge 44 of the locking tab 34. It will be realized that the outer end of the contacts G and P are semihemispherical in form which form is standard in the art. Accordingly the for ward sloping edge 44 is sloped to engage the sernihemispherical end of the contact G so thatupon such engagement the bias of the spring 50 is overcome and the forward extending portion 38 is forced or cammed downwardly so that its lower surface engages the lower arcuate surface of the tubular portion 29 of the female contact 20 and the upper edge of the end 42 is spaced below the upper arcuate surface of the tubular portion 29. Such engagement of the semihemispherical end of the contact G forces the lower surface of the locking tab 34 into engagement with the bottom arcuate surface of the tubular portion 29 of the contact 20 so that further longitudinal movement of the receptacle 2 towards the electrical plug '6 causes the contact G to slide the locking tab 34 rearwardly through the tubular portion 29 and the projection 46 through the slot 32 until the upper rearward edge of the projection 46 engages the outer surface of the body 14 and the lower rearward edge of the projection engages the end of slot 32. With the tab 34 so displaced the contact G has fully entered the tubular portion 29. Also as the contact G slides longitudinally into the contact 20 the power contacts P slide longitudinally within the tubular portions 28 of the contacts '18, respectively and properly establish all of the electrical circuits. It will be realized such longitudinal movement can only be accomplished by closing the spring 50' and according ly the coils of the spring 54) have a closed height to permit such displacement of the locking tab 34. The spring 50 is also of a structure so that it is normally extended to obtain the necessary forward biasing of the locking tab 34 as described.

In the event that the contact G is not in alignment with the female contact 20, or alternately stated, if any power contact P is aligned with the female contact 20 proper electrical engagement of the contacts P with the contacts 18 is not obtained. Thus referring to FIGURE 8 it will be noted that when any contact P is aligned with the female contact 20 the outer end of the receptacle 2 passes over the outer end of the female contact 20 until it engages the forward sloping edge of the projection 46. Upon such engagement between the face 5 of the receptacle 2 and the projection 46 the contact P has not electrically engaged the female contact 20. Upon further axial movement of the receptacle 2 over the female contact 20 the locking tab 34 is displaced rearwardly of the female contact 20. Such rearward displacement of the tab 34 eliminates the fulcrum at the forward end of the slot 32, however, the point of engagement between the face 5 with the forward sloping edge of the projection 46 establishes a new pivot point or fulcrum for the tab 34 so that the tab 34 is constantly biased in the clockwise direction by the spring 50. It will be noted that the outer ends of the openings 3 are suitably laterally enlarged so that the fulcrum provided thereby may be located as desired. By locating the fulcrum of the face 5 above the fulcrum of the tab 34 with the slot 32 the spring 50 exerts a greater clockwise biasing force on the tab 34 until the upwardly extending end 42 is in alignment with the forward slot 30 at which time, due to the clockwise bias of the spring 513, the forward end 42 enters the slot 3t) to prevent further inward movement of the plug 2 over the female contact 20. The spring 5i} thereafter continues to bias the end 42 into the slot 30 thereby latching or locking tab 34 with tubular portion 2? as shown in FIG. 9. At such time all the electrical contacts P, which are the same in length, are still spaced from any of the female contacts 18 and 2t? so that none of the electrical circuits connected to the contacts 18 and 20 are electrically energized. It will be realized that the ground contact G may enter one of the contacts 18 when a power contact P is aligned with the contact 20; however, since the contact G is grounded such engagement will not create any electrical hazard. Although the spring 50 can engage the projection in any suitable manner, as shown, the bottom edge of the surface on the back of the base portion 36 adjacent the projection 48, against which the last turn of the spring rests, is located forwardly of the back surface of the projection 46. Such location of such back surfaces shifts the effective point of application of the spring 50 forces up towards the top of the tab 34 and closer to the pivot point at the front end of the slot 32. Such force shifting is desirable in order that the end 42 is not biased upwards too strongly against the top of the contact 20 since excessive bias causes some difficulty with the ground contact G camming the tab 34 when the contact G is properly inserted. Thus the tab 34 is cammed well down, as shown in FIGURE 7, so that there is no possiblity of the end 42 catching in slot 30 (or any burr left on the edge of slot 30) when it is intended that the tab 34 should slide on by.

Disengagement of plug 6 from receptacle 2 merely requires that receptacle 2 be withdrawn longitudinally away from plug 6. Upon such withdrawal the ground contact G permits the locking tab 34 to move longitudinally outwardly in tubular portion 29 under the bias of spring 50 until the portion 52 of tab 34 engages the forward end of slot 3-2 as illustrated in FIG. 7.

If desired the receptacle 2 may be of a larger diameter than the shell -8 and be provided with annular longitudinally inwardly extending opening 51 for receiving the outer end of the shell 8 therein when the receptacle 2 engages the plug 6. It will be realized that the directional references such as upper, lower, inner, outer, etc. used herein have been employed for the sake of more concisely and clearly defining the structures of this invention; however, it will be realized the structure of this invention does not require such directions to be employed. Thus, it will be noted that this invention provides a single, inexpensive structure for preventing mis-mating of electrical contacts, and also this invention is applicable to a wide variety of contact structures.

Accordingly, having described a preferred embodiment of this invention in accordance with the patent statutes, it is to be realized that modifications thereof maybe made without departing from the broad spirit and scope of this invention. Accordingly, it is respectfully requested that this invention be interpreted as broadly as possible and as limited only by the prior art.

What I claim is:

1. An electrical contact comprising, an elongated open ended hollow portion, a locking tab axially slidable in said hollow portion, engageable means on said tab and said hollow portion for locating said tab axially with respect to said open end of said hollow portion, a portion of said engageable means on said tab extending laterally beyond the outer periphery of said hollow portion, said tab having a portion extending axially forwardly of said engageable means, means on said hollow portion engageable with means on said extending portion of said tab to prevent axial movement of said tab when said laterally extending portion of said tab is moved axially away from said open end, other means on said extending portion of said tab adapted to be engaged by a means inserted into said open end of said hollow portion for moving said tab axially within said hollow portion.

2. An electrical contact comprising, an elongated open ended hollow member having an elongated longitudinally extending first lateral opening spaced inwardly of an open end thereof, said member having a second lateral opening spaced intermediate said first opening and said open end, said first and second opening being longitudinally aligned, an elongated locking tab longitudinally slidably received in said member, said locking tab having forward and rearward portions, said forward portion being located at the end of said tab adjacent said open end of said member, said rearward portion being located at the other end of said tab remote from said open end of said member, said rearward portion having a projection extending laterally therefrom in longitudinal alignment with 7 said projection on said rearward portion, said projection on said rearward portion being contactable to cause said projection on said forward portion to engage said second opening whereby said tab becomes locked against longitudinal movement.

3. An electrical contact comprising, an elongated open ended hollow member having an elongated longitudinally extending first lateral opening spaced inwardly of an open end thereof, said member having a second lateral opening spaced intermediate said first opening and said open end, said first and second openings being longitudinally aligned, an elongated locking tab longitudinally slidably received in said member, said locking tab having forward and rearward portions, said forward portion being located at the end of said tab adjacent said open end of said member, said rearward portion being located at the other end of said tab remote from said open end of said member, said rearward portion having a projection extending laterally therefrom through said first opening, said forward portion having a projection extending laterally therefrom in longitudinal alignment with said projection on said rearward portion, said projection on said rearward portion being contactable to cause said projection on said forward portion to engage said second opening whereby said tab becomes locked against longitudinal movement, and means for biasing said locking tab in a longitudinal direction toward said open end.

4. An electrical contact comprising, an elongated open ended hollow member having an elongated longitudinally extending first lateral opening spaced inwardly of an open end thereof, said member having a second lateral opening spaced intermediate said first opening and said open end, said first and second openings being longitudinally aligned, an elongated locking tab longitudinally slidably received in said member, said locking tab having forward and rearward portions, said forward portion being located at the end of said tab adjacent said open end of said member, said rearward portion being locatedat the other end of said tab remote from said open end of said member, said rearward portion having a projection extending laterally therefrom through said first opening, said rearward portion being relieved at a location diametrically opposite said projection extending laterally therefrom, said forward portion having a projection extending laterally therefrom in longitudinal alignment with said projection on said rearward portion, said projection on said rearward portion being contactable to cause said projection on said forward portion to engage said second opening whereby said tab becomes locked against longitudinal movement, and means for biasing said locking tab in a longitudinal direction toward said open end.

5. An electrical plug having a mating end adapted to be mechanically and electrically connectible to a mating end of an elongated electrical receptacle having at least two longitudinally extending male contacts spaced inwardly of the'mating end thereof, one of such male contacts being located nearest to said mating end than the other of such male contacts, comprising: at least two elongated hollow members spaced inwardly of the mating end of said plug; each of said hollow members having its longitudinal axis normal to the mating end of said plug and being open on at least the end thereof adjacent said mating end of said plug; said hollow members being adapted to closely slidably receive such male contacts respectively when axially aligned therewith; one of said hollow members having an elongated longitudinally extending first lateral opening spaced inwardly of said open end thereof; said one of said hollow members having a second lateral opening spaced intermediate said first opening and said open end; said first and second openings being longitudinally aligned; longitudinally slidable means located within one of said hollow members; said slidable means having first and second longitudinally aligned spaced lateral projections; said first projection being axially slidable in said first opening; said second projection being engageable with said second opening; said slidable means being movable longitudinally away from said mating end of said plug when contacted by said one of such male contacts to permit mechanical and electrical connection of said plug and such receptacle; and said first projection being contactabl'e with the mating end of such receptacle when said one of said hollow members is aligned with the other of such male contacts whereby continued relative longitudinal movement between said plug and such receptacle causes said second projection to engage in said second opening thereby locking said means within said one of said hollow members thus preventing further relative longitudinal movement between said plug and such receptacle and the mismating of the respective contacts and hollow members. i

6. An electrical plug having a mating end adapted to be mechanically and electrically connectible to a mating end of an elongated eelctrical receptacle having at least two longitudinally extending male contacts spaced inwardly of the mating end thereof, one of such male contacts being located nearer to said mating end than the other of such male contacts, comprising: at least two elongated hollow members spaced inwardly of the mating end of said plug; each of said hollow members having its longitudinal axis extending substantially normal to the mating end of said plug and being open on at least the end thereof adjacent said mating end of said plug; said hollow members being adapted to closely slidably receive such male contacts respectively when axially aligned therewith; one of said hollow members having an elon gated longitudinally extending first lateral opening spaced inwardly of said open end thereof; said one of said hol low members having a second lateral opening spaced intermediate said first opening and said open end; said first and second openings being longitudinally aligned; an elongated locking tab being longitudinally slidably received in said one of said hollow members; said locking tab having forward and rearward portions; said forward portion being located at the end of said tab adjacent said open end of said one of said hollow members; said rearward portion being located at the other end of said tab remote from said open end of said one of said hollow members; said rearward portion having a projection extending laterally therefrom through said first opening; said forward portion having a projection extending laterally therefrom in longitudinal alignment with said projection on said rearward portion; said locking tab being movable longitudinally away from said mating end of said plug when the forward portion of said tab is contacted by said one of such male contacts to permit mechanical and electrical connection of said plug and such receptacle; and said projection on said rearward portion of said tab being contactable with the mating end of such receptacle when said one of said hollow members is aligned with the other of such male contacts whereby continued relative longitudinal movement between said plug and such receptacle causes said projection on said forward portion of said tabto engage in said second opening thereby locking said tab within said one of said hollow members thus preventing further relative longitudinal movement between said plug and such receptacle and the mismating of the respective contacts and hollow members.

7. An electrical plug having a mating end adapted to be mechanically and electrically connectible to a mating end of an elongated electrical receptacle having at least two longitudinally extending male contacts spaced inwardly of the mating end thereof, one of such male contacts being located nearer to said mating end than the other of such male contacts, comprising: at least two elongated hollow members spaced inwardly of the mating end of said plug; each of said hollow members having its longitudinal axis normal to the mating end of said plug and being open on at least the end thereof adjacent said mating end of said plug; said hollow members being adapted to closely slidably receive such male contacts respectively when axially aligned therewith; one of said hollow members having an elongated longitudinally extending first lateral opening spaced inwardly of said open end thereof; said one of said hollow members having a second lateral opening spaced intermediate said first opening and said open end; said first and second openings being longitudinally aligned; an elongated locking tab longitudinally slid-ably received in said one of said hollow members; said locking tab having forward and rearward portions; said forward portion being located at the end of said tab adjacent said open end of said one of said hollow members; said rearward portion being located at the other end of said tab remote from said open end of said one of said hollow members; said rearward portion having a projection extending laterally therefrom through said first opening; said forward portion having a projection extending laterally therefrom in longitudinal alignment with said projection on said rearward portion; means for biasing said locking tab in a longitudinal direction toward said open end; said locking tab being movable longitudinally away from said mating end of said plug when the forward portion of said tab is contacted by said one of such male contacts to permit mechanical and electrical connection of said plug and such receptacle; and said projection on said rearward portion of said tab being contactable with the mating end of such receptacle when said one of said hollow members is aligned with the other of such male contacts whereby continued relative longitudinal movement between said plug and such receptacle causes said projection on said forward portion of said tab to engage in said second opening thereby locking said tab within said one of said hollow members thus preventing further relative longitudinal movement between said plug and such receptacle and the mismating of respective contacts and hollow members.

8. An electrical plug having a mating end mechanically and electrically connectible to a mating end of an elongated electrical receptacle having at least two longitudinally extending male contacts spaced inwardly of the mating end thereof, one of such contacts being located nearer to said mating end than the other of such male contacts, comprising; at least two elongated hollow members spaced inwardly of the mating end of said plug; each of said hollow members having its longitudinal axis extending substantially normal to the mating end of said plug and being open on at least the end thereof adjacent said mating end of said plug; said hollow members being adapted to closely slidably receive such male contacts respectively when axially aligned therewith; one of said hollow members having an elongated longitudinally extending first lateral opening spaced inwardly of said open end thereof; said one of said hollow members having a second lateral opening spaced intermediate said first opening and said open end; said first and second opening being longitudinally aligned; an elongated locking tab longitudinally slidably received in said one of said hollow members; said locking tab having forward and rearward portions; said forward portion being located at the end of said tab adjacent said open end of said one of said hollow members; said rearward portion being located at the other end of said tab remote from said open end of said one of said hollow members; said rearward portion having a projection extending laterally th r from t ough d firs p n g; d r d portion having a projection extending laterally therefrom and longitudinal alignment with said projection on said rearward portion; means for biasing said locking tab, in a longitudinal direction toward saidopen end; said rearward portion being relieved at a location diametrically opposite said projection extending laterally therefrom;

said locking tab being movable longitudinally away from said mating end of said plug when the forward portion of said tab is contacted by said one of such male contacts to permit mechanical and electrical connection of said plug and such receptacle; and such projection on said rearward portion of said tab being contactable with the mating end of such receptacle when said one of said hollow members is aligned with the other of such male contacts whereby continued relative longitudinal move ment between said plug and such receptacle causes said projection on said forward portion of said tab to engage said second opening thereby locking said tab within said one of said hollow members thus preventing further relative longitudinal movement between said plug and such receptacle and the mismating of the respective contacts and hollow members.

9. An electrical plug having a mating end adapted to be mechanically and electrically connectible to a mating end of an elongated electrical receptacle having at least two longitudinally extending male contacts spaced inwardly of the mating end thereof, one of such male contacts being located nearer to said mating end than the other of such male contacts, comp-rising: at least two elongated hollow members spaced inwardly of the mating end of said plug; each of said hollow members having its longitudinal axis extending substantially normal to the mating end of said plug and being open on at least the end thereof adjacent said mating end of said plug; said hollow members having their ends remote from said mating end of said plug secured in spaced relationship to an insulating member within said plug; said hollow members being adapted to closely slidab-ly receive such male contacts respectively when axially aligned therewith; one of said hollow members having an elongated longtiudinally extending first lateral opening spaced inwardly of said open end thereof; said one of said hollow members having a second lateral opening spaced intermediate said first opening and said open end; said first and second openings being longitudinally aligned; and elongated locking tab longitudinally slidably received in said one of said hollow members; said locking tab having forward and rearward portions; said forward portion being located at the end of said tab adjacent said open end of said one of said hollow members; said rearward portion being located at the other end of said tab remote from said open end of said one of said hollow members; said rearward portion having a projection extending laterally therefrom through said first opening; said rearward portion being relieved at a location diametrically opposite said projection extending laterally therefrom; said forward portion having a projection extend-ing laterally therefrom in longitudinal alignment wtih said projection on said rearward portion; means for biasing said locking tab in a longitudinal direction toward said open end; said locking tab being movable longitudinally away from said mating end of said plug when the forward portion of said tab is contacted by said one of such male contacts to permit mechanical and electrical connection of said plug and such receptacle; and said projection on said rearward portion of said tab being contaotable with the mating end of such receptacle when said one of said hollow members is aligned with the other of such male contacts whereby continued relative longitudinal movement between said plug and such receptacle causes said projection on said forward portion of said tab to engage in said second opening thereby locking said tab within said one of said hollow members thus preventing further relative longitudinal movement between said plug and such receptacle and the mismating of the respective contacts and hollow members, i

10. An electrical contact comprising, an elongated open ended hollow portion, a locking tab axially slidable in said hollow portion, engageable means on said tab and said hollow portion for locating said tab axially with respect to said open end of said hollow portion, a portion of said engageable means on said tab extending laterally beyond the onterperiphery of said hollow portion, said by a means inserted into said open end of said hollow portion for moving said tab axially within said hollow portion. 11. An electrical contact comprising, an elongated open ended hollow member having an elongated longitudinally extending first lateral opening spaced inwardly of an open end thereoflsaid member having a second lateral opening spaced from said first opening in said open end, an elongated locking ta-b longitudinally slidably received in said member, said'locking tab having first and second projections, said first projection extending laterally beyond the outer periphery of said hollow member and being contactable to 'cause said second projection to engage said second opening whereby said tab becomes locked between longitudinal movement.

References (Iited in the file of this patent UNITED STATES PATENTS 11,425,049 Peterson Aug. 8, 1922 1,990,687 Godare Feb. 12, 1935 2,616,942, Simpson etal Nov. 4, 1952 2,935,724 Seifried et a1. May 3, 1960 

11. AN ELECTRICAL CONTACT COMPRISING, AN ELONGATED OPEN ENDED HOLLOW MEMBER HAVING AN ELONGATED LONGITUDINALLY EXTENDING FIRST LATERAL OPENING SPACED INWARDLY OF AN OPEN END THEREOF, SAID MEMBER HAVING A SECOND LATERAL OPENING SPACED FROM SAID FIRST OPENING IN SAID OPEN END, AN ELONGATED LOCKING TAB LONGITUDINALLY SLIDABLY RECEIVED IN SAID MEMBER, SAID LOCKING TAB HAVING FIRST AND SECOND PROJECTIONS, SAID FIRST PROJECTION EXTENDING LATERALLY BEYOND THE OUTER PERIPHERY OF SAID HOLLOW MEMBER AND BEING CONTACTABLE TO CAUSE SAID SECOND PROJECTION TO ENGAGE SAID SECOND OPENING WHEREBY SAID TAB BECOMES LOCKED BETWEEN LONGITUDINAL MOVEMENT. 